[repo] enhanced security handling: deprecates unsafe_execute, in favor of explicit read/write security control using the `enabled_security` context manager. Also code executed on the repository side is now unsafe by default.

from os.path import join
from cubicweb.toolsutils import create_dir

option_renamed('pyro-application-id', 'pyro-instance-id')

create_dir(join(config.appdatahome, 'backup'))